Chemical sorbents are used to capture carbon dioxide (CO2)
from flue gas through adsorption, absorption, or a combination of the
two. They can be arranged in various configurations, including fixed,
moving, and fluidized beds. Research projects in this pathway address
key technical challenges to sorbent-based systems, such as circulating
large quantities of solid particles for adsorption and regeneration,
sorbent attrition, large fluid gas volume, relatively low CO2
concentration, flue gas contaminants, and high parasitic power demand
for sorbent recovery. Brief descriptions of several National Energy
Technology Laboratory (NETL) Office of Research and Development projects
are provided below, followed by additional sources of information.

Reactor Design for CO2 Capture Using Sorbents
The focus of this research is to understand the impact of regenerable
solid sorbent systems on reactor designs. Key sorbent parameters have
been determined and will be considered including heat of adsorption,
heat capacity of the solid, delta CO2 loading between the adsorption and regeneration steps, and effect of acid gases within the flue gas.

Sorbent Development for CO2 Removal for Flue Gas Applications
Research for this project is focused on fabricating solid, high-surface
area substrates impregnated with various amine compounds that exhibit
higher CO2 capture capacities and lower regeneration temperatures than conventional amine-based liquid solvents.

Surface Immobilization Nanotechnology for CO2 Capture Sorbents
The use of surface immobilization nanotechnology to graft amine
compounds on a high surface area solid sorbent substrate to optimize CO2
capture is being examined in this research. The amine is grafted to
the sorbent by an electrostatic layer-by-layer self-assembly process.
This process provides control of coating thickness, uniformity, and
roughness on the nanometer scale.

CO2 Capture Sorbent-Based Device Simulation
Computational fluid dynamic models are being developed to evaluate the
performance of sorbent-based reactor designs. These simulations will be
incorporated into NETL’s advanced process engineering co-simulator
model for the full power plant.

Molecular Design and Evaluation of CO2 SorbentsNovel amine-enriched sorbents are being prepared through
chemical treatment of high-surface area materials with various amine
compounds for the capture of CO2. Increasing the surface area greatly reduces the volume of sorbent otherwise required.

Novel CO2 Capture Concept
The goal of this project is to investigate two CO2 capture
concepts: (1) utilization of an immobilized carbonic anhydrase (CA)
enzyme and (2) amine-enriched solid sorbents. The use of a CA agent
represents a novel approach to capturing CO2, while the addition of amine functionality to solid sorbents is anticipated to yield higher CO2
carrying capacities. One of the focuses in this research is to
understand the nature of grafted amine functional groups, due to their
role in determining the amount of CO2 being adsorbed.

Low Temperature Sorbent Development of CO2 Separation from Post-Combustion Gas Streams
The focus of this project is to test existing sorbents and to develop new materials for the capture of CO2
from both combustion and gasification effluent streams. These
sorbents will be tested for long-term durability. Additionally,
suitable binders will be investigated and tested to determine the effect
of the binders on sorbent performance.